Electron tube



Jan. 11, 1938. w. DALLENBACH ELECTRON TUBE Filed Dec. 21, 1934 2 Sheets-Sheet 1 lnventor: LUa/zer DH/enbach A Horneya Jan. 11, 1938. w. DALLENBACH 2,105,026

ELECTRON TUBE Filed Dec. 21, 1954 2 Sheets-Sheet 2 lnventor:

l/o/zer DOV/embody A izorneys anodes.

Patented Jan. H, 1938 NITED STATES amaze A PATENT OFFICE ELECTRON TUBE lands Application December 21, 1934, Serial No. 758,672 In Germany January 9, 1934 9 Claims.

The object of the present invention is an electron tube and, particularly, an electron source, which renders it possible to produce in the high vacuum a reliable two and polyphase rectifier with the aid of one hot cathode and two or more The electron tube in accordance with the present invention is further adapted for exciting, i. e. generating, amplifying and receiving, electro-magnetic oscillations, especially such of a very high frequency.- If in the electron tubes control grids are built in, the electron tubes may very well be employed as two and polyphase alternating current amplifiers.

It is known, that on the surface of a hot cathode accommodated in the high vacuum, an electric double layer in form of a positive surface charge and a negative space charge, situated in front thereof, is produced. In consequence of the negative space charge, a potential minimum, preventing the escape of further electrons from the hot cathode, will be caused on the emitting surface. For the purpose of being able to obtain with the aid of such hot cathode an emission, it is essential that this potential minimum is neutralized, at least partly, by subjecting the hot cathode and an anode, housed within the tube, to a voltage. This property of a hot cathode influenced by the space charge proves in many cases a disadvantage. It will, thus, for instance, be impossible to form, by means of a hot cathode and two or more anodes arranged in one and the same electron tube, a two or polyphase rectifier. The momentarily positively charged anodes possess, as a matter of fact, the tendency to press down the potential wall, impeding the escape of electrons from the hot cathode, the negatively charged anodes, however, acting in the opposite way, by neutralizing the effect of the positive anodes, with the result, that an emission from the hot cathode cannot take place.

This disadvantageous property of the hot cathode can be obviated, by providing, suitably in the immediate vicinity of the cathode, an exciting anode which, relatively to the hot cathode, is given only a low positive voltage, in order to render it possible to press down the potential wall of the cathode, preventing an escape of electrons. This will then be instrumental in producing a stream of electrons flowing from the hot cathode to the exciting anode situated in the vicinity, said stream of electrons then giving rise in connection with the employment of higher stream densities, to the formation of an electron 'cloud proper. This electron cloud, produced by the flow of electrons, subsequently serves as electron source.

The object of the present invention is, therefore, an electron tube, in which, according to the present invention, a flow of electrons, passing from a hot cathode to an exciting anode, is mad to serve as electron source.

As long'as an electron source of such description is not deprived of electrons, all electrons, emitted by the hot cathode, will pass, in form of the electron cloud referred to, over to the exciting anode provided in the vicinity of the hot cathode. If now, at a greater distance from an electron source of this description 2. further negatively charged electrode is arranged, this will now not be capable of preventing the emission of the hot cathode, inasmuch as the exciting anode, arranged in the immediate vicinity of the hot cathode and being charged positively relatively to the latter, will prove preponderant in its effect on the potential wall. If, on the other hand, this further electrode is charged positively, or, in other words, worked as anode, it will be capable of attracting electrons from the fiow of electrons at the expense of the exciting anode. 25 The arrangement thus permits of creating a two or polyphase rectifier, in which a plurality of anodes, arranged within one and the same electron tube, is made to cooperate with a common electron source, consisting of a fiow of electrons passing from the hot cathode and the exciting anode.

Examples of performance and examples of application of the present invention are represented by the Figs. 1-9. 35

Fig. 1av illustrates a rectifier tube with an arrangement of cathodes in accordance with the present invention in perspective view, Fig. 1b showing the same tube in section along the line Fig. 2 shows in graphic representation a similar rectifier tube, as detailed in Fig. 1 with a simplified arrangement of cathodes.

Fig. 3 is an example of performance of the 45 arrangement oi electrodes within a vacuum ves-' sel I has been provided, consisting of two barshaped parallel hot cathodes 2 and 3, an exciting anode 4, also bar-shaped and parallel to the former, and of two plate-like anodes 5 and 8. The two hot cathodes are conductively connected at their upper ends by means of a yoke I. For the purpose of fixing the cathodes, the yoke has been mounted upon the end of the exciting anode so as to be insulated therefrom. The hot cathodes are heated by means of the current source 8. The battery 9 is made to impart to the exciting anode a weak, positive bias. The two anodes have been connected with the secondary winding 01' a transformer I0. From the terminals 5! connected with the cathode and the symmetry point of the secondary winding, may be taken the output rectified in the tube.

It will be gathered from Fig. lb, that the hot cathodes and the exciter anode are made to consist of flat bars or hands, arranged within one plane at a small distance from each other. Such a design of hot cathodes and exciting anodes possesses, in contradistinction to bars of a round shape which, of course, can also be used, the ad-- vantage of a lower loss of leakage. The electrons passing from the hot cathodes to the exciting anode will then move along strongly curved paths, as characterized in Fig. lb by means of dotted lines. A deprival of electrons through the medium of the anodes proper will, be greatly facilitated thereby. In the illustrated example the two anodes 5 and 6 have been provided symmetrically to the arrangement of the cathodes and vertically to the plane placed through the latter, for the purpose of ensuring, above all, an arrangement stable against electrostatical forces.

In the example represented in Fig. 2, the arrangement of the cathodes also consists again of bar-shaped and parallel conductors H, l2 and i3, being arranged symmetrically to the two anodes 5 and 6. The intermediate electrode 52 has, in this instance, however, been galvanically connected at the upper end via a resistance It with the two electrodes ii and i3. If, for instance, the electrode |2 has been designed as hot cathode and its lower end connected with the negative pole of a source of E. M. F. not shown, whilst the lower ends of the electrodes H and I3 are connected with the positive pole of the source of E. M. F., the electrodes H and i3 will be given through the drop of potential at the resistance H a positive potential relative to the hot cathode. The electrodes Ii and I3 are serving for this reason in this instance not only as return path for the heating current of the hot cathode i 2, but also as Weakly positively biased exciting anodes. If the electrodes H and iii are also designed as hot cathodes and if an alternating potential is fed to the terminals l5 for heating purposes, the electrodes ll, l3 will be rendered negative during a semi-cycle, functioning as cathode, in which case the electrode I2 serves as exciting anode. During the other semi-cycle the electrodes ll, l3 and I2 change their roles, so

that each of the electrodes alternately fulfils the oi. this description J6 and II have been indicated in H8. 4.

The described novel electron source is particularly adapted for use in electron tubes, which are made to serve for exciting, i. e. generating, amplifying and receiving or ultra-high frequency oscillations. I The arrangement is of special interest for the region or the centimeter and decimeter waves; In view ot the fact, that the electron cloud, passing from cathode to the exciting anode, corresponds to a hot cathode with very high filament temperature, the electron source shows an inconsiderable inertia. For this reason it allows of being easily controlled, e. g. through the medium of control grids l6 and II as shown in Fig. 4 or by means of anodes 5 and 6 as for example shown in Fig. 1. A further consequence thereof is the reduction of the duration of transmission of the electrons from the'surface of the electron cloud to the more distant electrodes.

Fig. 3 represents a perspective view of a generator for ultra-short waves, the electro system of which corresponds to the cross section of Fig. 1. 2 and 3 are again hot cathodes, between which the exciting anode 4 has been arranged. The whole of this system, serving as electron source, is positioned between two conductors 5 and 6 of a Lecher system, the ends of which are serving as anodes at 5 and 6. The leads to the hot cathodes 2 and 3 and to the exciting anode 4 are placed in the symmetry plane between the two conductors 5 and 6 of the Lecher system. The extended anodes 5 and 5 are made to form a Lecher system of the length A, being galvanically overbridged at their lower end by means of a metal plate l8. On exciting the Lecher system a potential loop will be formed at its upper open end and a potential node of the oscillation at the lower short-circuited end. Through the medium of the source of E. M. F. IS the anodes 5 and 6 are jointly given a positive potential. The source of current serves, as in the example of Fig. 1, for the purpose of heating the hot cathodes 2, 3, and the source of E. M. F. for producing bias of the exciting anode. With the aid of the transformer 22 it will be possible to attain by means of a change of the potential between hot cathodes and exciting anode,

a modulation of the emission of the cathode arrangement. The feed of the D. C. potential to the anodes 5 and 5 is eiiected at the end it in the current loop of the Lecher system.

If the D. C. potential of the conductors 5 and 6 relatively to the electron source 2, 3, ii is so selected, that the duration of transmission of the electrons from the electron source to the conductors 5, 6 is comparable with the duration of cycle of the ultra-high frequency oscillations, the quarter wavelength of which corresponds to the length of the Lecher system, the Lecher system will be excited to oscillations through the medium of the flow of electrons.

The mode of operation of this excitation mechanism may be imagined to be as follows: If between the conductors 5 and 6 there already exists an ultra-high frequency oscillation, corresponding to the length of the Lecher system, at a given moment, at which 5 may be positive, 6, however, negative, most of the electrons being present in the vicinity of 2, 3, 4 are forced towards 5. The constant field existing between 2, 3, 4, on the one hand, and 5 on the other hand, now conveys these electrons to the electrode 5. During this transition of the electrons, however,

the electrode 5, in consequence of ultra-high frequency oscillation existing between the conductors 5 and 6, changes its polarity, so that the electrons are reaching the electrode 5. at a moment, at which the latter is already negative again. It is presupposed in connection herewith, that the constant field existing between the cathode arrangement 2, 3, l on the one hand and the anode 5 on the other hand, causes a duration of transmission of the electron, which is comparable with half the duration of cycle of the ultra-high frequency oscillation.

Instead of a single condensed wave of the electrons there may be along the path between the electron source 2, 3, '4 and one of the conductors 5 or 6 several of such waves. This will also be the case, if the D. C. potential of 5, 6 relatively to 2, 3, 4 is so selected as to be comparatively low. The oscillating system will then, as it is called, be excited in a lower oscillating zone. It is characteristic of a lower oscillating zone, that the duration of transmission of the electrons is'approximately an uneven multiple of the duration of transmission of the electrons of the first oscillating zone.

In this arrangement according to Fig. 3, the conductors 5 and 6 of the Lecher system are made to serve not only as anodes, but also as control electrodes. It will naturally also be possible to employ separate electrodes, as they have been represented in Fig. 4, in which case the resonator, containing the control electrodes, is coupled in a suitable manner with'the resonator containing the anodes.

According to the selection of the exciting potential, i. e. the potential between the hot cathode and the exciting anode, the flow of electrons passing over will be more or less intensive, in connection with which the hot cathode proper works in the space charge zone or in the saturation zone. As long as the excitation is effected in the space charge zone of the hot cathode, the exciting potential may serve for the modulation of the electron-flow passing over to the other electrodes present in the tube. For instance, in the transmitter in accordance with Fig. 3, the ultra-high frequent oscillating energy may be modulated by changing the exciting potential between th electrodes 2, 3 and 4.

Electron tubes with a flow of electrons as electron source are particularly adapted for amplifying purposes and also for simultaneously rectifying two or polyphase currents. If generally a p-phase alternating current is to be amplified and rectified by means of a tube, it is essential to arrange p-anodes and p-control grids around the source of electrons.

A tube, adapted for the amplification and rectification of a two phase alternating current by means of one tube and an electron source provided within said tube, is represented in section in Fig. 4. Apart from the electron source 23, two anodes 5 and 6 and two control grids l6, I! have been provided in addition.

The dependence of the anode current Ia upon the grid potential E; has been represented in Fig. 5. At a negative grid potential no current will flow to the anode appertaining to the grid. At a positive grid potential 9. current begins to flow to the appertaining anode, rising almost linearly, until practically all the electrons, under the influence of the exciting potential, are moving towards the anode with positive control grid. Subsequently the anode currentshows the characteristics of saturation. I

An example of performance for the purpose of amplifying a three-phase alternating current is shown in Fig. 6. 23 represents graphically the electrode arrangement, consisting of hot cathode and exciting anode, provided for the purpose of producing the flow of electrons. The battery 24 serves as source of current for heating the hot cathode and for biasing the exciting anode. Around the electron source 23 three grids 26 and behind these three anodes 26 have been symmetrically arranged. The grids are, for instance,

star-connected with the coil ends of the secondary winding 21 of an input transformer, whilst the anodes are star-connected in the same manner with the coil ends of the primary winding 28 of an output transformer. Furthermore, the cathode arrangement is connected with the starpoint 29 of the input side directly and with the star-point 30 of the output side via the source of E. M. F. 3|. Through the medium of the latter the anodes 26 are given a common positive bias.

For the sake of simplicity, two phase systems only have been represented in the examples of application of Figs. 7-9, although the performances are applicable analogously also for any desired p-phase systems.

Fig. 7 shows the cascade connection of two amplifying tubes 32 and 33. The electron source within the tubes will be produced by means of an electrode arrangement already shown in Fig. 2. Furthermore, grids and anodes have been provided within the tube according to Fig. 4. Via the terminals 34 the control potential is fed directly to the grids of the tube 32. The inductive potential divider 35 guarantees the uniform distribution of the control potential over the two grids, in view of the fact, that the symmetry point 36 is connected with the cathode. Furthermore, the anodes of the tube 32 are galvanically connected with the control grids of the following tube 33. By means of the battery 31 the anodes of the tube 32 are given a positive bias via the resistance relatively to the cathode arrangement. The anodes of the amplifying tube 33 are connected with the primary winding of an output transformer 39. Via the symmetry point 40 of the primary winding the anodes of the tube 33 are given a positive bias through the medium of the battery 4|. The terminals 42 can be used for supplying the amplified output. It is a matter of course, that also more than two tubes may be connected in series cascade-like.

In a similar manner as in the electron tubes known so far, it is also possible in this instance to utilize the phenomenon of the amplification for the improvement. The latter may be increased to such an extent, that the tube excites itself, working as oscillation generator. An arrangement of this kind has been reproduced in Fig. 8. 23 characterizes again the electron source, the control grids and 26 the anodes of the tube. As with the second cascade in accordance with Fig. 7 the plus-pole of the constant potential source 4| and the anodes are connected with the primary winding of a two phase transformer 39. For the purpose of taking off the amplified or the generated output, this transformer is coupled with an auxiliary winding 43, supplying the potential for the control grids. This potential shows in the usual manner a phase shift of 180 relatively to the anode potential, so that a control grid possesses at that moment its maximum positive potential, feeding the anode assigned to it with the maximum of electrons, because this anode assumes its lowest potential. Instead of the inductive cou- ;1 pling indicated iiiFig. -8, any other of the known kinds of coupling may be made use of. It is also possible, that a coupling is selected so loosely, that no self-excitation takes place, but, onthe other hand an enhanced amplification as in connection with a back-fed audion.

Fig. 9 shows an arrangement in which an al ternating current is amplified and, at'the same time, rectified. In the cathode line the primary winding 44 of a transformer has been connected in series with the direct currentfsource. If the amplitude of the A. C. potential/fed tothe terminals 34, is modulated, the rectified current flowing via 44 will be characterized by the identical modulation. Corresponding to this modulation a drop of potential will take place at the self induction 44, which may be used for taking ofl a modulation output. The energy is suitably taken off via the secondary winding 46 of the transformer 45. Instead of the transformer 45,. a resistance, interpolated in the circuit, may, naturally, also be made use of.

In the claims, the term exciting of ultra-high frequency electromagnetic oscillations is intended to mean generating, amplifying and receiving of such oscillations.

What I claim, is:

1. An electron tube comprising a receptacle having a high vacuum therein, a plurality of anodes within said receptacle, an incandescible cathode and an exciting anode intermediate said first anodes, current leads extending from one end of said cathode and exciting anode, and means connecting the other ends of said cathode and exciting anode together.

2. An electron tube comprising a receptacle having a high vacuum therein, a plurality of anodes within said receptacle, an incandescible cathode and an exciting anode intermediate said first anodes, current leads extending from one end .of said cathode and exciting anode, and electrical conducting means connecting the other ends of said cathode and exciting anode together.

3. An electron tube comprising a receptacle having a high vacuum therein, a plurality of.

electrodes within said receptacle, an incandescible cathode and an exciting anode located intermediate said first electrodes, said exciting anode being of band-like shape and mounted close .to-' gether with and in the same plane as said cathode.

4. An electron tube comprising a receptacle having a high vacuum therein, a plurality of anodes within said receptacle, an incandescible cathode and an exciting anode located intermediate said first anodes, said exciting anode being of band-like shape and mounted close together with andin the same plane as said cathode, a resistance element within said receptacle conductively connecting said cathode and said exciting anode at one end thereof, and current leads secured to the other ends of said cathode and said exciting anode. i

5. An electron tube comprising a receptacle having a high vacuum therein, a plurality of anodes within said receptacle, twoincandescible cathodes intermediate said anodes, an exciting anode intermediate said cathodes, said exciting anode being of band-like shape and mounted close together with and in the same plane as said cathodes, a resistance element within said receptacle conductively connecting said two cathodes with said exciting anode at one end thereof, and

current leads at the other ends of said cathodes and said exciting anode.

6. An electron tube comprising a receptacle having a high vacuum therein, a plurality of anodes within said receptacle, two incandescible cathodes and an exciting anode intermediate said anodes, said exciting anode being of band-like shape and mounted close together with and in the same plane as said cathodes, a resistance element within said receptacle conductively connecting sai'd cathodes with said exciting anode at one end thereof, and current leads at the other ends of said cathodes and said-exciting anode.

7. An electron tube comprising a receptacle having a. high vacuum therein, a plurality of anodes within said receptacle, a control grid, an

incandescible cathode and an exciting anode, said exciting anode located intermediate said first .anodes, said exciting anode and said cathode being substantially straight and parallel and mounted in the same plane.

8. An electron tube comprising a receptacle having a high vacuum therein, a plurality of anodes within said receptacle, a control grid, two incandescible cathodes mounted close together an electrode intermediate said cathodes, a resistance element within said receptacle conductively connecting said two cathodes at one end thereof and current leads at the other ends of said cathodes, whereby said cathodes alternately serve as an exciting anode and said electrode serves as a cathode.

9. An electron tube comprising a receptacle having a high vacuum therein, a plurality of anodes within said receptacle, two incandescible cathodes, an exciting anode located intermediate said cathodes, said cathodes and said exciting anode being of band-like shape and mounted parallel and in the same plane facing each other at their edges, a control grid, a resistance element within said receptacle conductively connecting said two cathodes with said exciting anode at one end thereof and current leads at the other ends of said cathodes and said exciting anode.

WALTER DKLLENBACH. 

